Finite Element Model for Analysis of Fission Gas Release from UO2 Fuel

摘要

A finite element model is proposed to analyze in-pile fission gas release from UO2 fuel. The model describes fission gas transfer from grain interior to grain boundaries by simul-taneous mechanisms of diffusive flow and boundary sweeping, considering the effect of irra-diation-induced resolution in grain boundaries. The onset of gas release is predicted when gas amount in grain boundaries is saturated. The grain is assumed to be spherical and is radially divided into a number of elements, in each of which the diffusion problem is approxi-mated by describing the gas concentration in terms of a quadratic function. The effect of grain growth is treated by updating the nodal radii incrementally. This model is applicable to variable irradiation histories and its required computer time is acceptable for use in fuel rod performance codes.